In South Carolina, several variations of flood hazards occur due to the different effects of severe thunderstorms, hurricanes, seasonal rains and other weather-related conditions. The State's low-lying topography, combined with its humid subtropical climate, makes it highly vulnerable to inland or riverine flooding. Riverine flooding occurs when the flow of rainwater runoff is greater than the carrying capacities of the natural drainage systems.
Floods develop slowly, while others such as flash floods, can develop in just a few minutes and without visible signs of rain. Additionally, floods can be local, impacting a neighborhood or community, or very large, affecting entire river basins and multiple states.
Flash floods can occur within a few minutes or hours of excessive rainfall, a dam or levee failure, or a sudden release of water held by an ice jam. Flash floods often have a dangerous wall of roaring water carrying rocks, mud and other debris. Overland flooding, the most common type of flooding event typically occurs when waterways such as rivers or streams overflow their banks as a result of rainwater or a possible levee breach and cause flooding in surrounding areas. It can also occur when rainfall or snowmelt exceeds the capacity of underground pipes, or the capacity of streets and drains designed to carry flood water away from urban areas.
Be aware of flood hazards no matter where you live or work, but especially if you are in low-lying areas, near water, behind a levee or downstream from a dam. Even very small streams, gullies, creeks, culverts, dry streambeds or low-lying ground that appear harmless in dry weather can flood.
- Avoid building in a floodprone area unless you elevate and reinforce your home.
- Elevate the furnace, water heater and electric panel if susceptible to flooding.
- Install check valves in sewer traps to prevent floodwater from backing up into the drains of your home.
- Contact community officials to find out if they are planning to construct barriers (levees, berms or floodwalls) to stop floodwater from entering the homes in your area.
- Seal the walls in your basement with waterproofing compounds to avoid seepage.
- Review your insurance policy. Flood coverage is not part of most homeowner, mobile home or renter’s insurance policies. There is a 30-day waiting period for coverage to take effect.
- Be aware of potential flash flooding. If there is any possibility of a flash flood, move to higher ground. Do not wait to be told to move.
- If time allows, prepare your home for a flood by moving essential items to an upper floor, bring in outdoor furniture, disconnect electrical appliances and be prepared to turn off the gas, electricity and water.
- Do not walk through moving water. Six inches of moving water can make you fall. If you have to walk in water, walk where the water is not moving. Use a stick to check the firmness of the ground in front of you.
- Do not drive into flooded areas. If floodwaters rise around your car, abandon the car and move to higher ground if you can do so safely. You and the vehicle could be quickly swept away.
- After a flood, listen for news reports to learn whether the community’s water supply is safe to drink.
- Avoid floodwaters; water may be contaminated by oil, gasoline or raw sewage. Water may also be electrically charged from underground or downed power lines.
- Be aware of areas where floodwaters have receded. Even if the roadway of a bridge or elevated highway looks normal, the support structures below may be damaged.
- Stay clear of downed power lines and report them to your power company.
- Use extreme caution when entering buildings; there may be hidden damage, particularly to foundations. Stay out of any building that is surrounded by floodwaters.
- Clean and disinfect everything that got wet. Mud left from floodwater can contain sewage and other harmful chemicals.